Concentration of ores



March 8, 1932-;

CONCENTRATION Filed Aug. 27, 1930 FCRUDE CRUSHED 0P5. CONTAIN/N6 OXIDE IAND SULPH/DE LCOPPER MINERALS J. L. STEVENS LEACHINGUI SOLUTION. (WATER,ACID z-rc.)

LEACH/NG APPARA 'rus FLEACHED ana AND LIQUOR "-1 WATER FOR l iCLASS/FYING L AND WASHING-J CLA SSIFY/NG AND WASH/N6 A PPARA TUS l f" 1l PULP CONDITIONING: WASHED I .sL/MEs AND LIQUOR I I METALLIC] I AGENTS.(LIME; COARSE I CARRYING DISSOLVED I mom I L cYANmE, ETC.) J Lsmvos LCOPPER FINE GRINDING A PPARA TUS- (ROLLS, MILLS, CLASS/FIERS,

APPARATUS FOR PREC/P/ TAT/N6 ETC. DISJOLVED COPPER f""""' I L "I l r 1FL 0 TA 7-1 01v 1 I GROUND 6L IME PULP FL on: 770M l PEA GENTS. I SAND lCARRY/N6 I REAGENTIS- I I (COLLECTOR, I LPULP I PRECIPITATED I(COLLECTOR: I L FHOTHER, ETC.)J| I COPPER LF'ROTHER, Erq I FL 0 TA T/a/vF'LOTA no/v APPARATUS APPARATUS l- "-1 1 LCONCENTRA TESJ LCONCENTRA TESJLTA IL/NGS I FLEACHING SOLUTION. I (WATER, I L 4cm, ETC.)

March 8, 1932.

J. L. STEVENS CONCENTRATION OF ORES Filed Aug. 27, 1930 I cRunE GRU-SHEDone I comm/mus 0x105 |AND SULPHIDE I COPPER MINERALS J 5 Sheets-Sheet 3i rscpssn qvsnslzs I l SCREEN ulvnsnslzs I I MA TERIAL I MATERIAL JLEACH/NG LEACHING APP/IRA rus APPARATUS TEE FOR '3 l cLAsslFvl/va l lLEACHED 0R5 1 L AND LIQUOR APP/1R4 TUS F 01-? SEPARA TING LEACH/NGLIQUOR FROM COARSE SOL/D8 I- I I WATER I coARsE I soL'lus J WASHING APPA RAT US AJHED COARSE SOLIDS LEACH/NG I F I LIQUOR I l I WASH LWA TERr I I LE'ACHED ORE NDIUO- LA LO RJ I AND WASH/N8 l CLASSIF'YING' A NDWASHING APPARATUS i SL/MES AND LIQUOR I CARRYING DISSOLVE'D l COPPER IMETALLIC IRON I APPARATUS FOR PRECIPITATING DISSOLVED COPPER I "'1 IsL/ME PULP FFLOTATION CARRYING l REAGENTS. 1 PRECIPITAT'ED I l(COLLECTOR, I co per. l I FROTHER, Era.) l L..... .I

FLOTATION APPARATUS I'- 1 I CONCENTRA T56 I l TAlLuvas INVENTOR James L.5761 6/75 ATTORNEY 1 ETAl-LIC I I IRON IN I l FORM OF LISTEE BALLS J 5Sheets-Sheet 5 '1 WATER FOR CLAGSIFY/NG LEACHING SOLUTION. WATER; ACID,ETC.

AND WASH/N6 I" I JLIME PULP CARRYING 1 PRECIP/TATED LOPPER GRINDINGMILL.

I CARRYING D153 OLVE D J. L. STEVENS CONCENTRATION OF ORES r I I SLIMESAND LIQUOR I COPPER l.

Filed Aug. 27, 1930 EGCHED OR 1 l AND LIQUOR [VD I MASTER/AL J 1LEACH/IVG APPARATUS CLASSIFYING AND -wAsm/vs APPARATUS I I I .J

FVVASHED COARSE I L 51mm MATERIAL CRUDE cRUsHED ORE I CONTAINING OXIDE IAND SULPHIDE I I FCLASSJFY'ING APPARA March 8 COPPER MINERALS L TOGETHERWITH PVRITE ILCONDITIONING I I TING I I I I NG TANK OR APPARATUS FORIco/vo/T/aNl/va THE I COLLECTING REAGENT sL/ME PULP coIvTm/w/vaCONDITIONED COLLEC LREAGENT I C 0ND! TIONI r. l I

FROTHING AGENT.

Patented Mar. 8, 1932.-

UNITED srarrzs PA ENT OFFICE CONCENTRATION OF ORES Application filedAugust 27, 1930. Serial'No. 478,185.

This invention relates to the concentration of copper bearing ores, andhas for its oh- I ject certain provisions for improved ecof nomicrecovery of the valuable constituents 'of complex ores containingsulphide and nonsulphide copper minerals.

In general, clean-sulphide copper minerals are readily amenable torecovery by the customary methods employed in the modem flotationprocesses, whlle certain non-sulphide copper minerals are quiterefractory and usually constitute the major portion of the tailingslosses.

The non-sulphide copper minerals are enerally referred to .as oxide, andinc ude various oxides, carbonates, silicates, etc. of copper.Hereinafter the term .oxide shall be employed to include the abovementioned class of non-sulphide copper minerals which readily formcopper sulphateby reaction with dilute sulphuric acid.

Many copper bearing ores, requiring concentration by flotation, containan appreciable amount of oxide copper together with copper sulphides andgangue sulphides such as pyrite, and in the concentration of such ores,it is frequently desirable to reject a sub- 1 stantial amount of thepyrite with the tailings. The present invention is particularlyadaptedto the treatment of such complex ore, and the specific exafmplegiven herein. is directed to an. ore of this type. However, theinvention in its broadest aspect contemplates the treatment of anycopper oxide bearing ore. f

The present invention, briefly described, consists of subjecting thetotal ore (crushed to a suitable size), or portions of such ore,

6 to an acid leaching operation (using sulthe" oxide copper, classifyingthe leached ore (including the solution or liquor formed duringleaching) so that-the dissolved copper is collected with the relativelyfine slime portion of the ore, precipitating'the dissolved copper in theslime pulp by action of a'suitable precipitant such as metallic iron,subjecting the slime pulp containing the copper precipitate to flotationto produce a copper bearing concentrate, and subjecting the coarsewashed phuric acid or'other suitable acid) to dissolve portion of theore treatment. ,4

In general, the major portion of the oxide copper of the ore is obtainedas dissolved copper in the slime pulp, while the major 5 portion of thesulphide copper, and of the pyrite when present, is collected in thecoarser portion.

, By classifying the leached ore, the dis-- solved copper may beconcentrated in a rela- 0 tively strong pulp solution which enables thesubsequent treatment to be carried out very e'fliciently Classifyingalso permits the clean washed coarse portion of the ore to be subjectedto any method of disposal or treatment 85 to which it is best adapted.For example, the coarse classified portion of an ore containing coppersulphide minerals andpyrite maybe crushed or ground to a suitable sizeand subjected to flotation treatment adapted to selectively concentratethe copper bearing minerals from the free p ite.

Methods for recipitatm dissolved copper in an ore pu p, followed yfloatation for its recovery together with thenatural sul- '75 phidesofthe ore are old in the art. For example, U. S. Pat. No. 1,268,940issued to B. H Dosenbach discloses such a process. However, prior to minvestigations, no..pro-

to any suitable separate vision had been ma' e for concentrating the 7dissolved copper with the fine slime portion of the ore pulp forseparate subsequent precipitation and recovery by flotation. Theadvantages of the present invention are shown in various ways: in somecases by 5.

reducing the amount of acid required; in some cases by eflectingmarkedly better recoveries of the copper; insome cases by permittingdifl'erent and separate treatment of the various classified products;and in some cases by markedly reducing the time and cost of the recoveryof the copper in the flotation operation.

According to a preferred embodiment of the invention, the separatetreatment of the 'coarse portion of the ore, after separating the slimepulp and dissolved copper therefrom and washing the coarse material,consists in ,grinding these coarse sands suflicient- 1y fine fortreatment by fiotation, and then subjecting this ground material to aseparate flotation operation. The separate flotation treatment of theoriginal slime pulp containing the precipitated copper, and of theground sands, leads to several practical advantages, by reason of thefact that these two materials differ considerably in composition andalso in physical characteristics, and consequently require somewhatdifferent condi-- tions for maximum efiiciency of concentration byflotation. For example, I find it ad vantageous in some cases tomaintain an acid condition in the slime pulp during flotation treatmentthereof, and an alkaline condition in the pulp obtained by grinding thecoarse material, during its flotation treatment. Furthermore, differentcollectors or other flotation reagents may be used, which areparticularly adapted to the concentration of copper in the two pulps. I

Other advantages will be obvious from the following description and fromthe results of tests as given hereinafter.

Figs. 1, 2, 3, 4 and 5 of the accompanying drawings are fiow sheetsshowing various schemes or arrangements which may advantageouslybeemployed in carrying out the present invention. In these drawings theapparatus employed, or the operations involved, are indicated bylegends, as are also the materials introduced into the process, thematerials, delivered from each stage'of the process to the next, and thefinal products obtained, so that the drawings are self-explanatory.However, the following general remarks may be made regarding the schemesillustrated in the several figures.

Fig. 1 illustrates the invention in its simplest form and correspondssubstantially to the general description. of the invention given above.

Fig. 2 illustrates the embodiment of the invention mentioned above, inwhich the treatment of the coarse portion of the ore obtained from theclassifying operation consists in grinding this material and thensubjecting it to a separate flotation operation.

, In this case the slime pulp containing dis-.

solved copper, delivered from the classifying apparatus, is subjected tothe same treatment as in Fig. 1, except that, by way of example, I haveindicated the use of metallic iron asa precipitant for the copper. Thecoarse sands, after washing, and after addition of suitable conditioningagents thereto for assisting in subsequent concentration of the copperbearing constituents by flotation, are ground to proper fineness and arethen subjected to a flotation'operation in the presence ofsuitablereagents, to produce a separate copper bearing concentrate.

A somewhat more elaborate scheme of treatment is illustrated in Fig. Inthis case the crushed ore is first screened, and the oversize andundersizematerials are leached separately. According to the particulararrangement shown, the oversize material is leached with acid todissolve oxide copper therefrom, and the resultin liquor,containing'some dissolved copper ut still containing excess acid, isseparated from the coarse solids and is used to dissolve a furtherquantity of oxide copper from the undersize material. The leachedundersize material, to-

gether with the leaching liquor, is classified and washed, to produce awashed sand product and, a product consisting, as before, of the slimestogether with the liquor containing dissolved copper. The leached coarsesolids from the oversize material are washed, and the wash water fromthis operation may advantageously be used to furnish part of the waterrequiredin the classifying and washing of the leached undersizematerial. The, washed sands obtained from the leached un-" dersizematerial are combined with the .separation of slimes, a lower'percentageof solids must be maintained in the classifying operation than isdesirable in the subsequent treatment of the slime pulp. In such cases ascheme such as shown in Fig. 4, which provides for thickening theclassified slime pulp and returning the overflow liquor from thethickener to the classifier in closed circuit, may be advantageouslyemployed. The scheme shown in Fig. 4 also provides for the return ofpart of the thickener overflow liquor to the leaching apparatus in orderto further reduce the amount of fresh water added during the leachingand classifying operations. Fig. 4 also provides for wetting the ore, ifdesirable, with fresh water prior to treatmentin the leaching apparatusand also provides fresh water for washing the coarse material in theclassifying and washing apparatus. Thev combined amounts of fresh water,going with the slime pulp from the classifier, added prior toclassification and used in washing the coarse material should .beregulated "to equal the amount discharged with the thickened slimes fromthe thickener.

The pro-wetting of the crushed ore with water prior toapplying theleaching acid is advantageous in hindering absorption of the acidsolution by the clean ore particles,

in cases where the ore is very dry and the major portion of the copperis present in the form of sulphide, with the oxidized copper occurringchiefly at the surfaces of the ore my invention to one particular oreand the results obtained, it being understood, however, that this isgiven only as an example and that the invention is not restricted to theuse of the specific reagents, nor to the particular proportions givenbelow. Fig. 5 represents the flow sheet of this particular applicationof the invention.

Treatment of crude are A sample of crude ore (crushed to approximatelyminus three-quarter inch size and containing ore material of variousdegrees of fineness ranging from three-quarter inch size to finematerial of a clay-like nature) consisting chiefly of schist andporphyry rock containing disseminated minerals of copper and iron; thecopper minerals consisting of chalcocite and small amounts of othersulphides such as chalcopyrite, etc., and various oxides such aschrysocolla, malachite, sulphate, etc., and the iron being in the formof oxides and sulphides but chiefly in the form of pyrite extensivelyintercrystallized with the chalcocite) was subjected to an acid leachusing sulphuric acid at the rate of six pounds per ton of ore inconjunction with just sufiicient water to completely cover the ore andgive the mass a semi-fluid consistency. The ore was given about tenminutes contact with the strong acid solution with intermittentstirring, after which suflicient water was added to permit separatingthe fine slime pulp by decanting and draining same, with the liquorcontaining the dissolved copper, from the coarse material. The coarsematerial was finally washed with fresh water and all wash waters addedto the slime pulp. The total volume of leaching solution and wash waterused in leaching, classifying and washing the ore was equivalent to therate of 0.66 of a ton of water per ton of original ore.

Original crude ore assay Per cent Oxide 0.17 Copper sulphide -i 0.75TotaL. 0.92 Iron (total) 4.31 Products of classification Copper per centWeight T 0t 31 of ol'lgliron Oxide sulphide Total Coarsematerial 85.6.052 .775 0.827 1.41 Slimes 14.4 s1 .60 1.47 3.34

Leached copper in solution shown as oxide per cent of ore sllmes. u

The above analysis of the products of classification show that about 73.8% of the oxide copper is concentrated with the slime material, andabout 88.5% of the copper sulphide together with about 88.8% of the ironis retained with the coarse material. The amount of pyrite in each ofthe above products of Treatment of coarse material The coarse materialwas crushed by rolls to approximately minus ten mesh. Lime, at the rateof one pound per ton of ore, was then added and the ore made up into apulp by addition of water. The ore pulp was then classified into sandsand (secondary) slimes by washingout the fines produced by the rolls.Lime at the rate of three pounds per ton of original coarse material wasadded to the classified sands and the sands ground (wet) in a pebblemill to a suitable size for flotation treatment. The classified(secondary) slime pulp was thickened and lime at the rate of one poundper ton of original coarse material added. Butyl Xanthate at the rate of0.05 pound per ton of original coarse material, in a crude aqueoussolution contain ing approximately one part of sodium thiocarbonate to2.34 parts of sodium butyl xanthate, was added tov the thickened(secondary) slime pulp and allowed two hours contact. The ground sandpulp and the (secondary) slime pulp were then combined and subjected toflotation treatment to produce a copper bearing concentrate; pine oilbeing employed in the flotation operation as needed to produce therequired froth.

Treatment of leached slimes The acid slime pulp containing dissolvedcopper was allowed to stand about three hours and was then placed in agrinding mill charged with a mixture of steel balls and pebbles andground until the dissolved copper was precipitated by action of the ironcontained in the steel balls. After precipitating the dissolved copper,the slime pulp contaming same was taken from the mill and subjected toflotation treatment to recover, as a flotation concentrate, both theprecipitated and natural sulphide copper contained in this 111 p T hemineral collecting agent employed in the flotation operation consistedof an organic compound formed by reaction between potassiuni ethylXanthate and sulphur monochloride; having the formula This new flotationagent is described in my pending patent application Ser. No. 332,741.Any suitable collecting agent may of course be employed. However, acollecting agent of this type is very attractive for this particulartype of ore pulp because its effectiveness is not destroyed by acid ormineral salts that might be present.

The above described collecting agent was employed at the rate of 0.26pound per ton of slimes; 50% being added to the pulp duringprecipitation and 50% just ahead of flotation. Smaller amounts of thisreagent have been found very eflective.

Pine oil was employed to give the required amount of froth duringflotation.

Flotation results This result includes part of the iron in the form ofiron salts from the metallic iron precipitant.

The percentage of solids contained in the slime pulp may be variedconsiderably according to the nature of the slimes of the ore treated.For slimes of a clay-like nature a pulp containing 15 to 20 per centsolids has been found satisfactory, both in the precipitating andflotation operations. In general, I prefer to maintain a high percentageof solids in the slime pulp in order to concentrate the dissolved copperin a small volume of pulp. However, the slime pulp should be quitefluid, and not contain a percentage of solids sufficiently high tohinder precipitation or flotation.

The presence of free acid in the slime pulp aids precipitation of thedissolved copper. In general, I prefer to apply suflicient acid to thetotal ore in the original leaching operation to supply free acid duringprecipitation. However, in case the initial acid should be exhausted inthe leaching operation, the desired amount may be added prior toprecipitation.

In some cases the presence of free acid in the slime pulp duringflotation is advantageous, and in case the initial acid added forleaching and precipitation should be exhausted prior to the flotationtreatment, fresh acid may be added at the flotation machine to supplythe desired amount in the flotation circuit.

A ball mill containing steel balls has been found satisfactory as anapparatus for precipitating the dissolved copper. Any other suitableapparatus and/or precipitant may, however, be employed. I have alsofound that satisfactory precipitation may be accomplished by agitatingthe slime pulp, containing the dissolved copper, with sponge orpulverized iron.

Any suitable flotation reagents and type of flotation apparatus may beemployed for recovery of a copper bearing concentric from the slimepulp. If the type of collecting agent described in the foregoingspecific example for treatment of the slime pulp be employed, it is notnecessary to alter the conditions of the pulp from the precipitatingoperation, for flotation treatment, as this type of reagent functionsvery effectively in an acid or neutral pulp and is not destroyed bymineral salts, such as, for example, ferrous sulphate formed duringprecipitation. This type of collecting agent, however, may in some casesrequire more agitation for proper dispersion throughout the pulp than isprovided for in certain types of flotation apparatus, be advantageouslypro-agitated with the reagent to effect proper dispersion prior toflotation treatment.

I claim:

1. A method of concentrating ores which comprises subjecting an ore,containing oxide copper minerals, to a leaching operation, classifyingthe leached ore so as to collect the dissolved copper with the slimeportion of the ore, precipitating the dissolved copper in the slime pulpand subjecting the slime pulp to a flotation operation for separation ofa copper bearing concentrate.

2. A method of concentrating ores which comprises subjecting an ore,containing oxide copper minerals, to a leaching operation in thepresence of sulphuric acid, classifying the leached ore so as copperwith a slime pulp containing the relatively fine portion of the ore,precipitating the dissolved copper in-the slime pulp as a metallicprecipitate and subjecting the pulp to a flotation operation forseparation of a copper bearing concentrate.

3. A method of concentrating ores which comprises subjecting an ore,containing oxide copper minerals, to a sulphuric acid leachingoperation, classifying the leached ore so as to collect the dissolvedcopper with slime pulp containing the relatively fine portion of theore, precipitating the dissolved copper in the slime pulp as a metallicprecipitate by action of metallic iron and subjecting the pulp to aflotation operation for separation of a copper bearing concentrate.

and in such cases the pulp may to collect the dissolved which comprisesclassifying an ore material,

leached by action of sulphuric acid and containing dissolved copper, soas to collect the dissolved copper with a pulp containing the relativelyfine portion of theore material and obtain a separate product containingthe relatively coarse portion of the ore material, precipitating thedissolved copper as a metallic precipitate by action of metallic iron,subjecting the pulp containing the metallic copper precipitate to aflotation operation for separation of a copper bearing concentrate, andsubjecting the separated relatively coarse portion of the ore materialto separate treatment. 6. A method of concentrating ores which comprisessubjecting an ore material containing oxide and sulphur copper mineralsto 4 a leaching operation, classifying theleached' ore so as to collectthe dissolved copper with a pulp containing the relatively fine portionof the ore and obtain a separate relatively coarse portion of the orematerial, precipitating the dissolved copper in the presence of the fineportion of the ore material, subjecting the pulp containing the copperprecipitate to a 'flotation operation for separation of a copper bearingconcentrate, grinding the separated relatively coarse ortion of the orematerial to a suitable size or flotation treatment, and subjecting theground coarse portion of the ore material to a separate flotationoperation for separation of a copper bearing concentrate. I

7. A method of concentrating ores which comprises subjecting an orematerial containing oxide and sulphide copper minerals to a sulphuricacid leaching operation, classifying. the leached ore so as to collectthe dissolved copper in a pulp containing the rel atively fine portionof the ore material and obtain a separate relatively coarse portion ofthe ore material, applyin metallic iron to the pulp comprising the eportion of the ore material to precipitate the dissolved copper,subjecting the pulp containing the metallic copper precipitate to aflotation operation to separate a copper bearing concen trate th pulpbeing in an acid condltion'during flotation, grinding the relativelycoarse portion of the ore material to a suitable size for flotationtreatment, and subjecting the ground coarse portion of theore materialto a separate alkaline flotation operation for separating a copperbearing concentrate.

8. A method of concentrating ores which comprises subjecting materialcontaining oxideand sulphide copper minerals together with pyrite to asulphuric acid leaching operation, classifying the leached material soas to collect the dissolved copper in a pulp containing the relativelyfine portion of the material and collect the major portion of the.

copper sulphide minerals and pyrite with the relatively coarse portionof the material, applying metallic iron to the pulp comprising the fineportion of the material to precipitate the dissolved copper, subjectingthe pulp containing the metallic copper precipitate to a flotationoperation to separate a copper hearing concentrate, grinding therelatively coarse portion of the material in the presence of added lime,and subjecting the ground pulp to a separate flotation operation forseparating a copper bearing concentrate from pyrite and other gangueconstituents of the material.

,9. In the concentration of ores, the system which comprises leaching anore containing both oxide and sulphide copper minerals, so

as to dissolve oxide copper, classifying the leached ore including theresulting solution so as to collect the dissolved copper with therelatively fine portion of the ore material and obtain a separaterelatively coarse ortion of the ore, precipitating the disso ved copperin the presence of the fine portion of the ore, and separately treatingthe relative 1y coarse portion of the ore and the relative ly fineportion containing the precipitated copper for separation of copperbearing concentrates.

In testimony whereof I have hereunto subscribed my name this 21st day ofAugust,

JAMES L. STEVENS.

Ill

